1. Field of the Invention
The present invention relates to the field of earth boring tools and more particularly to apparatus for recovering cores from rock formations.
2. Description of the Prior Art
Conventional core barrels normally dispose the cut core into a metal or hard synthetic resin tube which is axially disposed within the inner barrel of the coring tool. The coring tool or some portion therein is retrieved at the well's surface and the metal or hard synthetic resin tube used as a casing to retain the core within the tool during retrieval and thereafter for transportation to a laboratory. However, it is extremely difficult to recover undisturbed cores in a coring operation using metal or hard resin core tubes if the core is taken from a highly unconsolidated rock formation or the rock is badly fractured. Often, such broken cores jam or wedge in the metal or hard resin tube thereby stopping the coring operation.
What is needed is some type of coring tool design wherein the core may be kept intact, but where a badly fractured or unconsolidated core is accepted without a high risk of jamming.